Effect of calcium rich and alkaline solutions on the chemical behaviour of hemp fibres

David Sedan (1) , Cécile Pagnoux (2) , Thierry Chotard (1) , Agnès Smith (1) , Vincent Gloaguen (3) , Pierre Krausz (3)

1 GEMH - Groupe d'Etudes des Matériaux Hétérogènes
2 Axe 1 : procédés céramiques
3 LCSN - Laboratoire de Chimie des Substances Naturelles

Chemical reactivity of hemp fibres placed into a cimentitous matrix was studied by using a lime solution as a simplified cement solution. The hemp fibres contain 56.1 wt.% of cellulose, 20.1 wt.% of pectin, 10.9 wt.% of hemicellulose and 6 wt.% of lignin. These compounds are not solubilised in a basic medium rich in calcium but a part located at the fibre surface should be degraded. This treatment leads also to the decrease of the cristallinity index of the cellulose. Calcium ions adsorb in a large quantity onto the fibre surface due to the high concentration of pectin. The structure of the homogalacturonic part of pectin forms with Ca2+ a stable chelate called "egg-box", supporting cation adsorption. The fibres are then covered by Ca(OH)2 nodules after immersion in a lime solution.

Domaines: Matériaux; Matériaux

David Sedan, Cécile Pagnoux, Thierry Chotard, Agnès Smith, Vincent Gloaguen, et al.. Effect of calcium rich and alkaline solutions on the chemical behaviour of hemp fibres. Journal of Materials Science, 2007, 42 (22), pp.9336-9342. ⟨10.1007/s10853-007-1903-4⟩. ⟨hal-00203555⟩